Ability to build tag without "triggerOnPush"

### What feature do you want to see added?

Hi,
in the use case where I want to build **only** tags and branches under MR, without building EACH branch pushed, I've setup the plugin in following way:
```
triggers {
gitlab(branchFilterType: 'All',
excludeBranchesSpec: '',
includeBranchesSpec: '',
cancelPendingBuildsOnUpdate: false,
ciSkip: true,
noteRegex: '([Jj]enkins).*(retry).*',
pendingBuildName: '',
secretToken: '[REDACTED]',
setBuildDescription: true,
skipWorkInProgressMergeRequest: true,
sourceBranchRegex: '',
targetBranchRegex: '',
addVoteOnMergeRequest: true,
triggerOnAcceptedMergeRequest: false,
triggerOnApprovedMergeRequest: false,
triggerOnClosedMergeRequest: false,
triggerOnMergeRequest: true,
triggerOnNoteRequest: true,
triggerOnlyIfNewCommitsPushed: true,
triggerOpenMergeRequestOnPush: 'source',
triggerOnPush: false,
triggerOnPipelineEvent: false,
triggerToBranchDeleteRequest: false)
}
```
with this configuration I can buid branches under MR but tags cannot be built.

The only way to trigger tag builds is changing `triggerOnPush: false` to `true`, but the drawback is that EVERY pushed branch will be built (and it's something not wanted).

Is it possible to have a checkmark to explicitly select "Tag Push Event"?

Thanks.

### Upstream changes

_No response_

### Are you interested in contributing this feature?

I've no idea on how to contribute.